Low Latency Queuing is almost identical to CB-WFQ. However with LLQ , you can instruct one or more class-maps to direct traffic into a priority queue.
Realize that when you place packets in a PQ , you are not only allocation a bandwidth amount for that traffic but you are also performing policing (that is limiting the available bandwidth for that traffic).
Why are we policing ?
This is necessary to prevent higher-priority traffic from starving out lower-priority traffic.
Please also consider that if you give priority to multiple class-maps , the packets assigned to will go into the same queue.Packets which are queued in the priority queue can’t be fragmented , which is a consideration for slower links.
LLQ is the cisco preferred queuing method for latensy-sensitive traffic such as voice and video.